Using video memory as a ramdisk in Linux

An old idea hit me again recently: Why can’t you use the memory that’s sitting unused on your video card (unless you’re playing Doom) as a ramdisk? It turns out you can, just not if you’re using Windows. Some Linux people have been doing <a href=”http://hedera.linuxnews.pl/_news/2002/09/03/_long/1445.html”>it</a> for two years.<p>Where’d I get this loony idea? Commodore, that’s where. It was fairly common practice to use the video RAM dedicated to the C-128’s 80-column display for other purposes when you weren’t using it. As convoluted as PC video memory is, it had nothing on the C-128, where the 80-column video chip was a netherword accessible only via a handful of chip registers. Using the memory for anything else was slow, it was painful, but it was still a lot faster than Commodore’s floppy drives.<p>

So along comes someone on Slashdot, asking about using idle video memory as swap space. I really like the idea on principle: The memory isn’t doing anything, and RAM is at least an order of magnitude faster than disk, so even slow memory is going to give better performance.<p>

The principle goes like this: You use the Linux MTD module and point it at the video card’s memory in the PCI address space. The memory is now a block device, which you can format and put a filesystem on. Format it ext2 (who needs journaling on a ramdisk?), and you’ve got a ramdisk. Format it swap, and you’ve got swap space.<p>

The downside? Reads and writes don’t happen at the same speed with AGP. Since swap space needs to happen quickly both directions, this is a problem. It could work a lot better with older PCI video cards, but those of course are a lot less likely to have a useful amount of memory on them. It would also work a lot better on newer PCIe video cards, but of course if your system is new enough to have a PCIe card, it’s also likely to have huge amounts of system RAM.<p>

The other downside is that CPU usage tends to really jump while accessing the video RAM.<p>

If you happen to have a system that has fast access to its video RAM, there’s no reason not to try using it as swap space. On some systems it seems to work really well. On others it seems to work really poorly.<p>

If it’s too slow for swap space, try it as a ramdisk. Point your browser cache at it, or mount it as /tmp. It’s going to have lower latency than disk, guaranteed. The only question is the throughput. But if it’s handling large numbers of small files, latency matters more than throughput.<p>

And if you’re concerned about the quality of the memory chips on a video card being lower than the quality of the chips used on the motherboard, a concern some people on Slashdot expressed, using that memory as a ramdisk is safer than as a system file. If there’s slight corruption in the memory, the filesystem will report an error. Personally I’m not sure I buy that argument, since GPUs tend to be even more demanding on memory than CPUs are, and the consequences of using second-rate memory on a video card could be worse than just some stray blips on the screen. But if you’re a worry wart, using it for something less important than swap means you’re not risking a system crash by doing it.<p>

If you’re the type who likes to tinker, this could be a way to get some performance at no cost other than your time. Of course if you like to tinker and enjoy this kind of stuff anyway, your time is essentially free.<p>

And if you want to get really crazy, RAID your new ramdisk with a small partition on your hard drive to make it permanent. But that seems a little too out there even for me.

Caveats with LCD flat-panel monitors

I just took a phone call from someone who bought an LCD flat-panel and couldn’t figure out why it looked so great in the store but was purely horrible on his PC at home.

He ran into a bunch of problems that some might instinctively avoid but to others would be much less than obvious.Native resolution. LCD monitors have a native resolution, unlike CRTs. What that means is while a CRT can produce a range of pixels (dots) horizontally and vertically, an LCD has a fixed number of them. So if you buy a monitor whose native resolution is 1152×864 and you set it to 800×600, the display is going to be chunky and pixelated.

Refresh rate. We’ve been conditioned to look for high numbers for refresh rate, and to set it as high as possible. LCDs don’t refresh, so you’re supposed to set the refresh rate to 60 Hz. Feed a flat panel something other than a 60 Hz signal, and who knows what will happen? Some cope, some don’t. Keep it at 60 to be safe.

Video memory. This was the real problem-causer. What happens when you buy a new 19-inch LCD and plug it into a aged Pentium II-400? Well, the video card didn’t have enough memory to do any better than a 256-color display. When you’re used to 16-bit color, the loss of color depth is enough to offset the sharpness.

So when buying an LCD for an aged system, it makes sense to go ahead and pick up a new video card while you’re at it. An ATi Radeon 7000-based card has plenty of memory to do high-color displays at resolutions like 1280×1024 and higher, and at Newegg.com’s $27 price, they’re a cheap upgrade. Newegg has several other cards in that price range as well. Radeons have 32 megs; they also have a SiS-based card with 64. The Radeon is probably a bit better for games, while the SiS will give you higher-color displays at high resolutions. Frankly, for a low-end system I’d probably buy whichever card happens to be cheapest to ship.

DVI or traditional VGA? DVI gives a straight digital signal, as opposed to translating to and from analog. A DVI port on the monitor and on the video card usually costs extra, but if you want the best possible display, it may be worth the extra money to you.

Straight talk on cheap laptops

I’ve been getting lots of traffic ever since we started talking about the Sotec 3120x laptop here last week. It looks like an era of inexpensive laptops is about to arrive, because the Sotec isn’t your only choice.
Sam’s Club sells a variant of the 3120x for about the same price as Wal-Mart, but it comes with a 30GB drive in place of the 20.

Steve DeLassus tells me a number of places have been hawking Toshiba Satellite 1115-S103 laptops in the sub-$1000 price range after coupons and rebates and other marketing gyrations. Suggested retail price on it is $1099. Street price should be $1049 or lower, as that’s Toshiba’s price if you buy direct. Toshiba’s offering a $200 mail-in rebate. So at the very worst, you can get a Satellite 1115-S103 for $849 if you buy it direct from Toshiba.

And then I did some checking on a hunch. Dell’s offering its Inspiron 2650C for $899 ($849 through 12/11). HP is offering its Compaq Presario 905us notebook with an Athlon XP 1400, 256 MB RAM, DVD, 14.1″ LCD for $999 with a $100 rebate. The HP Pavilion ze4101 has a faster processor but less memory, for the same price. There are some variants on the HPs and Compaqs out there–you might not find in stores exactly what HP’s selling direct, but you’ll find something awfully close.

The Toshiba and Dell offer a bigger screen (14.1 inches), DVD drives, 256 MB RAM (the Dell has 128), and the other expected gizmos like modem and networking, along with a seemingly faster 1.5 GHz Celeron processor.

Which brings up a point.

The 1.5 GHz Celeron is based on the P4 architecture. Remember, at 1.5 GHz, the P4 is a dog. The Celeron is a castrated P4. The P4-based Celeron doesn’t start to give decent speeds until it hits 2 GHz. Even though the Celeron 1.5 has a 300 MHz advantage over the older P3-based Celeron 1.2, the “slower” Celeron will actually be faster. And less expensive.

The HP/Compaq models offer truly faster AMD Athlon XP CPUs and ATI Radeon mobility video chipsets.

I know people are going to ask me which one to buy. So let’s agonize together.

Durability: Toshiba, Dell, HP and Compaq all had decent service records in the past and there are lots of places that will work on them. Sotec is more of an unknown in the United States at this point.

Dell has traditionally had the best reputation, but their laptops didn’t fare well this year in PC World’s service and reliability roundup. HP and Toshiba were the best of this bunch. Now that HP and Compaq are the same company, the Compaq should fare well too.

Frankly, I’d buy an extended warranty with any of them, and count on it breaking at least once. That’s par for the course with a laptop, especially if you use it for what it’s intended, which is carrying it around a lot.

Performance: The 1.5 GHz Celeron in the Toshiba and Dell models is a notoriously bad performer. The 1.2 GHz Celeron in the Sotec is a good performer but the integrated video will hurt. The HPQ models use AMD Athlon XP CPUs and ATI Radeon Mobility video chipsets. Performance on the latest 3D games will disappoint (but LCD screens in general are bad for 3D gaming). But for light gaming and everything else someone might want to do, the HP and Compaq models will be great.

Input: The Sotec offers a slightly reduced keyboard with an at-times quirky layout. The others offer full-sized keyboards. All use touchpads; they’ll be decent but you’ll probably want to pick up a USB mouse with any of them to use at least part of the time. Touch-typists will prefer anyone but Sotec. Hunt-and-peck types probably won’t care much one way or the other.

Portability: The Sotec weighs 4.4 pounds. The others weigh in at 6.5 or 6.9 pounds. None are hogs, but some people will really like the svelte Sotec. The Sotec has a longer battery life. Advantage: Sotec.

Expandability/extras: The Toshiba, HP and Compaq models offer TV-out, which isn’t something everybody needs, but when you want it, you want it. It allows you to use a big-screen TV for presentations in a pinch. You can connect up a TV to the laptop and do digital slideshows for a bigger audience than can crowd around a laptop screen, which is nice if you’re into that kind of thing. And when hooked up to a TV, it can serve as an emergency DVD player.

The Toshiba offers two PCMCIA slots. Everyone else offers one. HP and Compaq memory maxes out at 1024 MB, while memory on the Toshiba and Dell max out at 512 MB to the Sotec’s 384 MB. HP, Compaq, and Sotec are all using shared video memory, so they’ll steal a little system memory to give to the video chip. Toshiba and Dell aren’t doing this. All have built-in USB 1.1 and networking; none offer built-in Firewire.

HP offers the fastest CPU of the bunch, and CPU upgrades in laptops are always questionable.

Advantage: HP.

Serviceability: The Sotec’s DVD/CD-RW drive and hard drive are bolted in, rather than being plug-in modules. It’ll be a lot harder to fix yourself if need be. On most other companys’ models (I don’t know about any of these for certain), the drives slide out easily for replacement. Replacement CD/DVD drives are a pain to track down after the fact for any laptop more than a year or two old, but the big name brands will almost certainly be easier. If you buy an extended warranty, fixing it is someone else’s problem, at least for a couple of years. Advantage: Everyone but Sotec.

Overall winner: Hard to say. The Sotec is designed to be a subnotebook; the others are entry-level full notebooks. If portability and versatility are important to you, get the Sotec. It’s the only one of the bunch that’ll burn CDs for you at this price point. Keep in mind that the Sotec’s combo DVD/CD-RW drive will wear out quickly if you use it to watch a lot of movies, and that replacing it won’t be terribly easy, as it’s not a slide-in module like costlier notebooks use. If you intend to watch a lot of movies on the Sotec, make sure you buy an extended warranty on it.

The Sotec has a couple of question marks, but it also has an awful lot going for it.

The HP and Compaq models have the best combination of serviceability, expandability, speed, and reliability. I don’t think I’d mess with the Toshiba or Dell unless their prices dropped considerably. Between Compaq and HP, HP gives you the faster CPU, while Compaq gives you the bigger hard drive and more memory. It’s easier to add memory and replace the hard drive than it is to upgrade a laptop CPU; I’d get the HP and add memory to it pretty quickly and plan on replacing its hard drive with a large 5400 RPM model in a couple of years. With its best-of-class CPU and video and upgraded someday with a faster hard drive, the HP ought to be a good performer for many years. If the Sotec’s question marks scare you, the HP offers a compelling alternative.

Future outlook: When a system reaches a magical price point (notables were the $899 all-in-one Compaq Presarios in 1996, the $399 eMachine in 1998, the $199 Microtel Linux PCs from Wal-Mart this year, and this year’s sub-$900 laptops) it’s extremely tempting to run out and buy one. Especially the Sotec, which offers not only a great price, but almost every possible extra.

But remember what happened in the past. Compaq invaded Packard Bell’s territory in 1996 and released an underpowered but reliable and capable PC for $899, complete. Almost immediately, everybody was selling PCs for under $1,000. Then along came eMachines, deciding that even $499 wasn’t cheap enough and offering a unit, again underpowered, for $399. Few matched eMachines’ price point, but most companies were soon offering something for $499.

Laptops aren’t going to bottom out at $849. There’s no point in putting a smaller screen or hard drive in that Sotec. But if Wal-Mart decides it wants a bottom-feeder laptop, it could have Sotec substitute a VIA C3 chip for the Celeron (the Celeron’s being phased out anyway, and Wal-Mart already sells C3-based machines and their sales have proven you don’t have to have Intel Inside in order for people to buy them), and replace the combo DVD/CD-RW drive for a straight DVD drive or even a straight CD-ROM drive. A Sotec 3120x variant with an 800 MHz C3 and a plain old CD-ROM drive could probably sell for $749 or even $699. If Wal-Mart decides to thumb its nose at Microsoft and offer a Linux-based variant, it could chop another $100 off the price. (The big question there is whether it’s possible to support the Sotec’s modem under Linux.)

How soon will it happen? Hard to say. But think about it. Wal-Mart undercut everybody. Everybody reacted quickly. Dell wants to own the laptop market, because it’s part of the PC market. Wal-Mart wants to own every market. They’ll both strike back. HP and Toshiba won’t throw in the towel right away either, because they’re both big in retail laptops.

Right now the Sotecs are selling like crazy. Wal-Mart and Office Depot can’t keep them in stock. They won’t lower prices any further unless Dell and HPQ and Toshiba react again and seriously cut into sales. That’ll depend on whether they’re satisfied with their current sales figures. With 14 shopping days until Christmas (and realistically, the clock running out on shipping something to arrive before Christmas), I don’t expect pricing or inventory conditions to change much in the next two weeks.

But remember, this is Christmas boom time. People always cut prices after Christmas to spur sales. Chipmakers cut their prices too, meaning these laptops will be cheaper to make a month from now.

So if you’ve been wanting a laptop for a while and the sudden appearance of $849 laptops got you thinking but you’re willing to wait a while longer, this is a good time to wait.

Another RISC platform for Linux

Vintage workstations. I’ve read two articles this past week about running Linux or another free Unix on vintage hardware.
http://www.debianplanet.org/article.php?sid=605
http://www.newsforge.com/article.pl?sid=02/02/19/049208&mode=thread

And while I can certainly appreciate the appeal of running a modern free Unix on a classic workstation from the likes of DEC or Sun or SGI, there’s another class of (nearly) workstation-quality hardware that didn’t get mentioned, and is much easier to come by.

Apple Power Macintoshes.

Don’t laugh. Apple has made some real dogs in the past, yes. But most of their machines are of excellent quality. And most of the appeal of a workstation-class machine also applies to an old Mac: RISC processor, SCSI disk drives, lots of memory slots. And since 7000-series and 9000-series Macs used PCI, you’ve got the advantage of being able to use cheap PC peripherals with them. So if you want to slap in a pair of 10,000-rpm hard drives and a modern SCSI controller, nothing’s stopping you.

There’s always a Mac fanatic out there somewhere willing to pay an exhorbinant amount of money for a six-year-old Mac, so you won’t always find a great deal. Thanks to the release of OS X (which Apple doesn’t support on anything prior to the Power Mac G3, and that includes older machines with G3 upgrade cards), the days of a 120 MHz Mac built in 1996 with a 500-meg HD and 32 megs of RAM selling for $500 are, fortunately, over. Those machines run Linux surprisingly well. Linux of course loves SCSI. And the PPC gives slightly higher performance than the comparable Pentium.

And if you’re lucky, sometimes you can find a Mac dirt-cheap before a Mac fanatic gets to it.

The biggest advantage of using a Mac over a workstation is the wealth of information available online about them. You can visit www.macgurus.com to get mainboard diagrams for virtually every Mac ever made. You can visit www.everymac.com for specs on all of them. And you can visit www.lowendmac.com for comprehensive write-ups on virtually every Mac ever made and learn the pitfalls inherent in them, as well as tips for cheap hardware upgrades to squeeze more speed out of them. I learned on lowendmac.com that adding video memory to a 7200 increases video performance substantially because it doubles the memory bandwidth. And on models like the 7300, 7500, and 7600, you can interleave the memory to gain performance.

Besides being better-built than many Intel-based boxes, another really big advantage of non-x86 hardware (be it PowerPC, Alpha, SPARC, MIPS, or something else) is obscurity. Many of the vulerabilities present in x86 Linux are likely to be present in the non-x86 versions as well. But in the case of buffer overflows, an exploit that would allow a hacker to gain root access on an Intel box will probably just crash the non-x86 box, because the machine language is different. And a would-be hacker may well run into big-endian/little-endian problems as well.

http://homepages.ihug.com.au/~aturner/7200boot.html

WordPress Appliance - Powered by TurnKey Linux